High energy hydrocarbon fuel containing magnesium alloys



3,lli,i-i-5 Patented Jan. 30, 1952 3,019,145 HIGH ENERGY HYDROCON FUEL CONTAEN- ING MAGNESIUM ALLOYS Lawrence Whitby, Midland, Mich assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed May 5, 1958, Ser. No. 732,790

14 Claims. (Cl. 149-87) This invention relates to high energy fuels, and more particularly to a high energy fuel comprising a hydrocarbon liquid and a magnesium product dispersed in said hydrocarbon and method for its preparation.

The importance of high energy fuel has increased considerably with the development of jet and rocket engines. To develop high speeds and high thrusts with rocket or jet engines high energy fuel is essential. In addition to the high energy content, the fuel must be chemically and physically stable. Also, it must be such that it can be easily stored and handled. Further the fuel must be readily ignitable and must be capable of being metered as a fluid into the combustion chamber of the engine without the need of complicated mechanical devices.

The heats of oxidation of certain light metals and metalloids, such as magnesium, aluminum, calcium, silicon, and boron, are so high either in terms of heat content per unit weight of fuel or per unit Weight of oxygen, or both that they possess a great potential value in providing increased range and thrust when used as fuels in propulsion units such as jet, ram-jets, or after burners. In order to obtain complete and rapid combustion of the metals or metalloids, they must not only be introduced into the combustion zone in extremely fine state of subdivision, but means must be found for their production and handling in such finely divided state without hazard, since in the dry state they are pyrophoric.

It is, therefore, an object of this invention to provide a high energy fuel which will meet the requirements set forth above containing a magnesium alloy or a magnesium compound or mixtures thereof and a method for its preparation.

The high energy fuel of the invention comprises a hydrocarbon liquid, a dispersant dissolved in said liquid, and a friable low ductility magnesium containing alloy or compound, such as the brittle magnesium alloys of calcium, aluminum, or silicon, intermetallic compounds of magnesium with aluminum or calcium, and magnesiumboron compounds, dispersed therein as relatively equiaxed particles of less than 1.0 micron in size.

It has been discovered that within certain limits, as defined below, magnesium may be alloyed or combined with calcium, aluminum, silicon, or boron to form highly friable products that may be dispersed in hydrocarbon liquid by grinding, as by ball-milling. The solid metal 's readily reduced by the grinding operation in the hydrocarbon liquid to particles of sub-micron dimensions. The

resulting dispersions at concentrations of the dispersed phase of from 20 up to about 60% by weight form high energy fuels which are mobile, pumpable liquid'rnixtures,

and readily ignitable.

The term magnesium alloy as used herein, means based upon the weight of alloys having a calcium content of from 15 to weight percent with the range of calcium from the eutectic at 16.3 weight percent of calcium to about 45 weight percent, the intermetallic compound Mg Ca, being particularly suitable; magnesium-silicon alloys having a silicon content of from 3 to 60 weight percent; and magnesium-boron compounds corresponding to MgB MgB and MgB Of the friable, low ductility magnesium alloys or compounds, the magnesium-calcium alloys and the magnesium-aluminum alloys are preferred. These metals have a low density and burn with a high heat output.

A hydrocarbon liquid, such as benzene, toluene, and light petroleum fractions, such as gasoline, kerosene, diesel fuel, and fuel oils used at present as jet engine fuels, may be used as the hydrocarbon liquid in the high energy fuel. The term light petroleum fraction as used herein means the known petroleum fractions having an API gravity of 30 degrees or higher.

A dispersant chemically inert With respect to the magnesium alloy or compounds and soluble in the hydrocarbon liquid is incorporated into the dispersion. The dispersant adsorbs with preferred orientation upon the surface of the particles preventing agglomeration of the particles and thus considerably decreases the viscosity and improves the pumpability of the dispersion. Illustrative examples of suitable dispersants are lecithin; certain sorbitan esters, such as sorbitan trioleate; hydrocarbon liquid soluble substituted oxazolines, such as 2-heptadecenyl-4-methyl-4-methanol-2-oxazoline; dioctyl ester of sodium sulfosuccinate; polyoxyethylene lauryl ether; and propylene oxide stearyl ether. Other dispersing -With these dispersants, the dispersions have relatively lowviscosities which remain remarkably constant over prolonged storage periods. Only a small amount of the dispersant need be used. However, the amount of the dispersant used is generally from 1 to 10 weight percent, the hydrocarbon liquid. A preferred amount is from 4 to 6 weight percent. dispersant is preferably added to the hydrocarbon liquid prior to comminuting the alloy. The high energy fuel is made most often by intermixing relatively large particles of the alloy with the hydrocarbon liquid and then comminuting the alloy in the mixture to the required particle size in admixture with the hydrocarbon liquid. The employment of a dispersant during the comminution results in a dispersion having smaller sized particles and considerably lower viscosity for a given concentration of the dispersed phase than that of a dispersion obtained without using a dispersant in the grinding operation. The dispersant, by being adsorbed upon the surface of the particles,prevents both pressure welding of the particles under the impact of grinding and also agglomeration of the particles.

Upon comminution of the friable low ductility magnesium alloys or compounds relatively equiaxed particles are obtained. -These particles are readily combustible and when dispersed in the combustible hydrocarbon liquid in presence of a suitable dispersing agent do not greatly increase theviscosity of the liquid. When non-friable alloys or metals, for example magnesium or aluminum, are comminuted, relatively large plate-type particles are obtained which greatly increase the viscosity of the disersion, compared to that of a dispersion having the same metal concentration. but with metal particles in equiaxed form. Thus by using a friable alloy, yielding equiaxed particles on grinding,

the concentration of the ground particles in the hydrocarbon liquid may be increased The 3 up to about 60 weight percent without increasing the viscosity of the mixture to the extent that it cannot be easily pumped or handled.

In addition to obtaining a particular type of particle for controllin the viscosity of the dispersion, the particle 5 about 96 hours depending upon the particle size of the size of the di spersed alloy must be less than 1 micron. alloy charged tothe mill and particular millemployed. The preferred particle size is in the range of 0.1 to 0.5 For example, particles of the magnes um a lurru-num can; micron. It is clear that rapid and complete combustion Pound 1 1 1z avefaglng 150 mlcfons u h is facilitated by extremely small particles and, morea 5.126 111 h a g .9 M9 y f over, smaller particles will settle less rapidly than larger for 96 m m a m m Wlth im i particles. However, it is well-known that dispersions of aiumlfla 2 3) l df o a out the same P311113 solid particles in a continuous liquid phase will settle when 8126 in 48 hours y g a steel mill wlth harden the particles have a higher density than the liquid. This Steel. ballstendency may be offset by incorporating in the fuel a The Hg ex mples further illustrate the invention gelling agent which increases the thixotropy or pseudot are n t to be construed as limiting 1t thereto. plasticity of the dispersions. Dispersions with thixotropic or pseudo-plastic rheological characteristics show a rela- Example, tively high apparent viscosity at low shear rate, but the V A high energy fuel according to the invention was apparent viscosity is greatly-reduced when the rate of prepared and the viscosityjof thisfuel compared to the shear is increased. Thus, such dispersions are highly visviscosity of a dispersion made of pure magn sium cous at rest, a condition which suppresses settling, but on In making this comparison, pellets of a magnesium shaking or stirring they become fluid. Small'quantities alloy containing' 17 percent calcium, the balance being of certain metal soaps, for example aluminum stearate magnesium, having a particle diameter in the range of. and aluminum octoate, are suitable gelling agents forthe 7 150 microns We re intermixed with approximately an equal above purpose. These may be incorporated into the dis weight of kerosene which contained about 6 weight perpersions by adding them as powders into the mixture cent of sorbitantni-oleate. This mixture was charged to pr or to comminution or they may be mixed into the hya steel ball mill and ground therein for 48 hours when drocarbon liquid containing the dispersant using gentle the particles of the alloy were reduced to a size in the heat to effect complete solution or dispersion rapidly. A range of 0.1 micron Theyiscosity of the slurry so ob suitable concentration of gelling agent has been found to tained was determined by a Brookfield torque-tube visbe from 0.25% to 1% based on the weight offthe hydrocometer to be 1090 centipoises at 25 C. at 12 rpm carbon liquid. r Thisjfuel slurry was readilysprayed and ignitable and To obtain magnesium alloy or compoundparticles of burned with intense heat. a the required size, ball-milling may be used. Generallya For comparison, in place ofthe friable magnesium-cal ground or atomized powder or milling chips, such'asvery" cium alloy, pellets of relatively pure magnesium alsohavfine lathe turnings of the alloy, are niixedwith' an inert ing .a particle size of approximately 150 microns were. liquid containing a dispersant," such as"previously do; used. The mixture of the magnesium and kerosene conscribed, and charged to a ball mill wherethe required size taining the sorbitan tri-oleate. was ball nrilled as abovereduction is obtained. Any liquid inert to the magnesium After 48 hours of milling the particle size was found to alloy or compound may be used as'the grinding. fluid be about 1.3,microns and-the mixture was paste-like, its. provided the dispersant is soluble therein. However, the viscosity being too high to be measu yi fifllq hydrocarbon liquid which will be employedin the high] describedahove. energy fuel is most often used. Thus, thegijindi lgand, i Example 11 mixing operations are combined andthe highenergy "fuel 46 1 Obtained after the Commimltion, e e yf pp o i-f In a manner similar to that described in Example I, mately equal weights of the magnesium product and hy-i high energy fuels were prepared from two magnesium-caldroc'ar'bo'n liquid are used. A fuel containing a smaller cium alloys one, A, containing 15 weightpercent and the amount of the alloy may be simply obtained by diluting other, B, containing weight percent of calcium respecthe concentrated comminuted product with more hydro-"50 tively, the balance being magnesium. These fuels were carbon liquid. If the grinding liquid used is not the hycompared to two similar dispersions obtained usingmagdrocarbon liquid which is to be a part of the fuel, the comnesium-calcium alloys containing less than '15 weight perminuted alloy is separated front the grinding fluid after cent of calcium. In the preparation of each of the fuels, the grinding, by various means apparent to those skilled the magnesium-calcium alloy as pellets having a particle in the art such as filtration, and intermixedwith the hysize in the range of150 microns was placed in the ball drocarbon liquid which is desired to be a partof the fuel. mill with kerosene and ball-milled for 48 hours. Other Also, in order to obtain a dispersion in a liquid too vispertinent details of Example II are shown in the table cous for elfective ball-milling, without heating'the ball below. It will be noted that with the magnesium-calcium mill, a dispersion in a low-boiling vehicle, such asben alloys containing 8.4 and 3.6 weight percent calcium; rezene,'may be prepared. This dispersion may be then spectively, and the balance magnesium, the dispersions obmixed with the appropriate amount of the relatively vi's- 4 cous liquid finally desired and the benzene distilled off from the mixture.

The time required to reduce the particle size of the alloy to the desired size may vary from a few hours to t ained were paste-like.

Magnesium Product Dispersed Amount of Brookfield V Amount. Particle V Dispersant,- Apparent of Solids Size or Dispersant Wt. Percent, Viscosityat in Fuel, Solids, Based on 12 r p.m., Alloy Composition Wt. Per- Micron Hydrocarbon Oentipolses cent; e Liquid A 15 Ca, Balance Mg... 45 0. l5 2-heptadiclnyl-4-methyl- 6 1,340. 7 a i4i-nmethano1-2-oxazoe. B 45 Ca, Balance Mg...- 50 6 1,525.

'Blank--. 8.4 Ca, Balance Mg- 50' a 6 Paste-like.

Blank--- 3.6 Ca, Balance Mg... '50 6 D0.

In a manner similar to that described in Example I, high energy fuels of magnesium-silicon alloys one, C, and the other, D, containing 37 and weight percent dispersant dissolved therein and a magnesium-calcium alloy containing from 85 to 55 weight percent of magnesium and from to 45 weight percent calcium in the form of relatively equiaxed particles of from 0.1 to 0.5

silicon respectively and the balance magnesium were pre- 5 mlcron m slze m an.am9unt of froln to l pared These fuels were compared to a dispersion com percent of the fuel, said dispersant being chemically inert taining 2 weight percent silicon which gave a paste. Wlth respect to magllesmm prqduct and aqsorbed Kerosene was used as the hydrocarbon liquid and the upon l of .sald qqmaxgd pamcles preventmg alloy particles having an initial particle size in the range glomemtlm. pamcles of 150 microns were ball-milled for 48 hours. Other 10 fluid hlgh energy .conslsts essenuany pertinent data of Example III are shown in table below: of a light Petroleum fractlon'comammg from 1 to 10 Magnesium Product Dispersed A t P til grnount ott lirookfiel? moun BI 09 ISDBISRD pparen of Sfiplids giiedof Dispersant W15. Pedrcent, \iizscosityat 111 119 01 S, ase OH I.D.1I1. Alloy Composition Wt. Pei Micron Hydrocarbon Oentipoises cent Liquid 0 37 Si, Balance Mg 50 0. 5 Dioctyl ester of sodium 5 650.

sulffosuccinate. D 10 Si, Balance Mg 50 0. 8 Sorbiton Trioleate 4 820, Blank--. 2 Si, Balance Mg 50 1.0 Dioctyl ester of sodium 6 Paste-like.

sulfosuccinate.

Example IV weight percent of a dispersant dissolved therein and a In a manner similar to that described in Example I, four high energy fuels containing a magnesium-aluminum alloy were prepared. The magnesium-aluminum alloys used contained 15, 32, 65, and 67 weight percent aluminum respectively and the remainder magnesium. Pertinent details and data are shown in the table below:

magnesium-aluminum alloy containing from 15 to 86 weight percent magnesium and 85 to 14 weight percent aluminum dispersed in said light petroleum fraction as relatively equiaxed particles of less than 1 micron in size in an amount of from 2 0 to 60 weight percent of the fuel, said dispersant being chemically inert with re- .Amount of Amount of Particle Dispcrsant, Brookfield Magnesium Product Solids in Size of Dispersant Wt. Percent, Apparent Dispersed Fuel, Wt. Solids, Based on Viscosity Percent Micron Hydrocarbon at 12 r.p.m.

Liquid 15 Al Balance Mg 55 0.7 Sorbitontrioleate (5 950 32 A1: Balance Mg 50 0.2 2-heptad1c1nyl-4-methyl-4- 6 1, 530

methanol z-oxazoline.

A], Balance Mg 60 0- 5. 4 2,210 67 Al, Balance Mg 0- 2 ec lll 6 1, 720

What is claimed is:

l. A fluid high energy fuel which consists essentially of a combustible hydrocarbon liquid containing a dispersant dissolved therein and a friable low ductility magnesium product selected from the group consisting of alloys and intermetallic compounds of magnesium with calcium, aluminum, silicon, and boron, in the form of relatively equiaxed particles less than 1.0 micron in size in an amount of from 20 up to 60 weight percent of the fuel, said dispersant being chemically inert with respect to the magnesium product and adsorbed upon surface of said equiaxed particles preventing agglomeration of said particles.

2. A fluid high energy fuel according to claim 1 wherein the hydrocarbon liquid is a light petroleum fraction containing from 1 to 10 weight percent of a dispersant dissolved therein.

3. A fluid high energy fuel, which consists essentially of a light petroleum fraction containing from 1 to 10 weight percent of a dispersant dissolved therein and a magnesium-calcium alloy containing from 85 to 20 weight percent magnesium and from 15 to 80 weight percent calcium in the form of relatively equiaxed particles of less than 1 micron in size in an amount of from 20 to 60 weight percent of the fuel, said dispersant being chemically inert with respect to the magnesium product and adsorbed upon surface of said equiaxed particles preventing agglomeration of said particles.

4. A fluid high energy fuel, which consists essentially of kerosene containing from 4 to 6 weight percent of a spect to the magnesium face of said equiaxed of said particles.

6. A fluid high energy fuel according to claim 5 wherein the light petroleum fraction is kerosene containing from 4 to 6 weight percent of sorbitan trioleate dissolved therein, as a dispersant, the magnesium-aluminum alloy is the intermetallic compound Mg A and the particle size is in the range of 0.1 to 0.5 micron.

7. A fluid high energy fuel, which consists essentially of a light petroleum fraction containing from I to 10 weight percent of a dispersant dissolved therein and a magnesium-silicon alloy containing from 40 to 97 weight percent magnesium and 3 to 60 weight percent silicon dispersed in said light petroleum fraction as relatively equiaxed particles of less than 1 micron in size in an amount of from 20 to 60 weight percent of the fuel, said dispersant being chemically inert with respect to the magnesium product and adsorbed upon surface of said equiaxed particles preventing agglomeration of said particles.

8. A process for the preparation of high energy fuel, which comprises comminuting a friable low ductility magnesium product selected from the group consisting of alloys and intermetallic compounds of magnesium with product and adsorbed upon surparticles preventing agglomeration calcium, aluminum, silicon, and boron, in an organic particles of said magnesium product in a hydrocarbon liquid in proportions such that the resulting mixture contains from 20 to 60 weight percent of the magnesium product.

9. A process for the preparation of a high energy fuel, which comprises intermixing a hydrocarbon liquid containing a soluble dispersant with a friable low ductility magnesium product selected from the group consisting of alloys'and intermetallic compounds of (1) magnesium-aluminum mixtures containing from 14 to 85 percent aluminum, (2) magnesium-calcium mixtures containing from to 80 weight percent calcium, and (3) magnesium-silicon containing from 3 to 60 weight percent silicon and intermetallic compounds of magnesiumboron corresponding to the formula MgB MgB and MgB in proportion such that the resulting mixture contains from to 6 0 weight percentof said magnesium 7 product and comminuting the magnesium product whil in the liquid until the particle size of the magnesium product is reduced to from 0.1 to 0.5 micron, said dispersant being chemically inert with respect to the magnesium product and adsorbed upon surface; of said equik axed particles preventing agglomeration of, said particles.

10. A process according to claim 9' wherein the hydrocarbon liquid is a light petroleum fraction containing from 1 tofl0-weightpercentof sorbitan trioleatedissolved therein, as. a dispersant.

11. A process according to claim 10 wherein the friable lowductility.magnesium product is a; magnesiumcalcium alloy containing'frorn 85 to 20 weight percent magnesium and from 15 to weight percent calcium.

12; A process according to claimlO wherein the friable low ductility magnesium product is a magnesiumaluminum alloy containing from 15 to 86 weight percent magnesium arid from 14 to weight percent aluminum.

13. A process according to claim 10 wherein the friable low ductility magnesium product is a magnesium boron compound.

14. A mobile, pumpable liquid high energy fuel according to claim 4 wherein the dispersant is Z-heptadicinyl-4-methyl-4-methanol-2-oxazoline.

References Cited in the file ofv thispatent UNITED STATESPATENTS 1,532,930 ONeill Apr. 7, 1925 2,477,549 Van Loen'en' July 26, 1949 2,573,471 Malina et al. 'Oct. 30, 1951 2,579,257 'Hansley Dec. 18-, 1951* 2,890,108

7 REFERENCES Anderton: Aviation Week, Nov. 12, 1956, pages 51, 53, 55, 43rd Report of National Advisory Committee for Aeronautics (1957), pages 2-4.

Frazier: Proceedings 14th Annual Meeting, Metal Powder-Association, April"21-3,' 1958, pages 65--70 Toulmin June 9, 1959- 

1. A FLUID HIGH ENERGY FUEL WHICH CONSISTS ESSENTIALLY OF A COMBUSTIBLE HYDROCARBON LIQUID CONTAINING A DISPERSANT DISSOLVED THEREIN AND A FRIABLE LOW DUCTILITY MAGNESIUM PRODUCT SELECTED FROM THE GROUP CONSISTING OF ALLOYS AND INTERMETALLIC COMPOUNDS OF MAGNESIUM WITH CALCIUM, ALUMINUM, SILICON, AND BORON, IN THE FORM OF RELATIVELY EQUIAXED PARTICLES LESS THAN 1.0 MICRON IN SIZE IN AN AMOUNT OF FROM 20 UP TO 60 WEIGHT PERCENT OF THE FUEL, SAID DISPERSANT BEING CHEMICALLY INERT WITH RESPECT TO THE MAGNESIUM PRODUCT AND ADSORBED UPON SURFACE OF SAID EQUIAXED PARTICLES PREVENTING AGGLOMERATION OF SAID PARTICLES. 